The 4-nitroimidazole compound and salt thereof represented by the general formula (2),
[wherein, X is a halogen atom or a group of the formula —S(O)n—R1; n is 0 or an integer of 1 or 2; and R1 is a phenyl group which may have 1 to 3 substituents, selected from the group consisting of a nitro group, a halogen atom and a lower alkyl group, in the phenyl ring],is a useful compound as intermediate for synthesis of various pharmaceuticals and agricultural chemicals, particularly, as intermediates for preparing antitubercular agents.
Up to now, methods for preparing 4-nitroimidazole compound of the general formula (2) are known, for example, methods shown by the following Reaction scheme-1 and Reaction scheme-2. [Cf. Jerzy SUWINSKI, Ewa SALWINSKA, Jan WATRAS and Maria WIDEL, Polish Journal of Chemistry, 56, 1261-1272, (1982)].

In the Reaction scheme-1 and -2, XA is a halogen atom.
However, these methods involve several drawbacks, thus, they are not suitable for industrially applicable methods of preparation. For example, in the method shown by Reaction scheme-1, compound (6) and compound (7) as intermediates for the reaction are chemically unstable compounds, thus these compounds are in danger of explosion caused by shocks of dropping, frictions and others. Further, in the reaction for introducing compound (7) by heating (at about 130° C.) compound (6), this temperature exceeds TNR temperature (Temperature of No Return: an allowable maximum temperature around 60 to 70° C., at which the compound (6) can be handled safely in a chemical process equipment), for this reason, this method involves very danger for conducting in a large scale industrial production of these objective compounds.
While, in the method shown by Reaction scheme-2, the reaction is a nitration of a compound (8). However, by this nitration, the objective compound (2a) can be only obtained in low yield, thus this method is industrially disadvantageous.